Year 2009, water quality sonde data.15 minute readings of water column temperature, salinity, oxygen and depth in the upper Parker River Estuary at Middle Rd Bridge, Newbury, MA
Measurements are made using a YSI 6600 water quality datalogging sonde. YSI Sonde sensors consist of 6150 optical dissolved oxygen probe , 6560 conductivity/temperature probe (thermistor) and non-vented** cable with level depth sensor (stainless steel strain gauge).
Missing data or blank values are caused by maintenance time periods or where sensor measurements are obviously wrong in the context of what would be expected. For example, the conductivity sensor has a relatively small opening and chamber for the conductivity electrodes, the estuary can have varying suspended sediment/detrital loads moving in the water column which enter the conductivity cell shorting out the electrodes making a faulty conductivity measurement (lower than expected). Oxygen measurements are dependent upon the conductivity measurements so the oxygen also becomes erroneous.
Obvious measurements/data errors have been removed from the data set however the user of this data should also conduct their own data analysis to determine if the data are suitable for their particular situation. Typical sensor/data problems are:
For oxygen: Poor/inaccurate conductivity measurements will affect the dissolved oxygen accuracy
For conductivity: Conductivity cell can have detrital material stuck in it, shorting out cell, resulting in lower than expected conductivity.
For depth: Depth strain gage pressure sensor may come out of the water at low tides resulting in many "zero" depth readings or sometimes negative values. YSI Dissolved oxygen % saturation reporting can vary depending upon how the oxygen is calibrated.
For this data set two Oxygen percent saturation values are reported.
ODO%YSI variable name represents a YSI calibration in air, from Standard Methods, refers to calibration at a particular ATM pressure which allows DO% for calibration to fluctuate above/below 100% when ATM is above/below reference 760 or 1 ATM
ODO%Local variable name represents an oxygen calibration in air at a particular ATM pressure but it forces the DO% to be 100%, does not allow it to be under or above if ATM is above/below 760. ODO%Local data should be used for metabolism studies when correcting for diffusion based on gradient deviations from 100% which by definition is the % saturation of oxygen in air. ODO%YSI should not be used since it would require a known ATM pressure at each interval to calculate the ATM % saturation of oxygen to be use for that interval, probably a small correction anyway. Concentration of DO remains the same for either calibration.
**Depth values needed corrections factors applied due to using a non-vented cable with the YSI.
Pressure/depth readings needed a post deployment correction to account for changes in ambient atmospheric pressure. Marshview Farm (MFM) weather station 15 minute barometric pressure data was used to compute correction factors at the same time intervals as the 6600 sonde time intervals.
Ambient pressure changes correspond to the following water level changes, 1 mb = 0.0102 meters of water.
To correct our non-vented sonde depth readings for atmospheric pressure effects, we correct the sonde to 1 standard atmosphere (1013 millibars or 760 mm Hg) when we calibrate it, then apply an offset to the depth data (post collection) based on simultaneous measures of barometric pressure
2009 Depth Correction factor calculations for Middle Rd
Sonde is calibrated in air at ambient pressure and should be calibrated to the corresponding depth at pressures relative to 1 ATM (760torr or 1013.25 mBar. 1mB = 0.0102 meters of water, 1 Torr = 1.333224 mB. If ambient air is 1014.58 mB pressure then sonde should be calibrated to 0.0136 m.
Example table is below.
For 5/12/2009 the sonde depth was incorrectly calibrated to 0.000(m) instead of 0.0816(m). The error has been corrected/accounted for in the data file.
Table of Middle Road Bridge sonde depth calibrations by date for 2009
Using the table above and measured depth data for the corresponding time intervals with pressure units in mB
Corrected depth (m) = (Measured depth + Offset) - ((Measured BAR- std ATM or 1013.25) x 0.0102)
Version 01: March 5, 2012, updated data and metadata. Used MarcrosExportEML_HTML (working)pie_excel2007.xlsm 28/12 8:18 PM for QA/QC to EML 2.1.0
Version 02: May 29, 2014, updated data and metadata to comply with importation to Drupal and LTER PASTA. Used MarcrosExportEML_HTML (working)pie_excel2007.xlsm 5/28/14 2:09 PM for QA/QC to EML 2.1.0
Version 03: May 30, 2014, 5/30/14 edited metadata/data for correct atm correction (1013.25mB not 1013), data and metadata comply with importation to Drupal and LTER PASTA. Used MarcrosExportEML_HTML (working)pie_excel2007.xlsm 5/28/14 2:09 PM for QA/QC to EML 2.1.0